Lawmakers gave a standing ovation to the 69-year-old Nobel peace laureate and current Myanmar opposition leader, who could not collect the prize 23 years ago for being under house arrest.
"We have made progress since 1990, but we have not made sufficient progress," Suu Kyi, who was freed in 2010, told the European Parliament.
Suu Kyi: Right to live with a conscience has to be preserved
"Our people are just beginning to learn that freedom of thought is possible, but we want to make sure that the right to think freely and to live in accordance with a conscience has to be preserved," she said.
"This right is not yet guaranteed 100 percent. We still have to work very hard before the basic law of the land, which is the constitution, will guarantee us the right to live in accordance with our conscience. That is why we insist that the present constitution must be changed to be a truly democratic one," Suu Kyi said.